ternary tungsten boride nitride (WBN) thin films and related methods of formation are provided. The films are have excellent thermal stability, tunable resistivity and good adhesion to oxides. Methods of forming the films can involve thermal atomic layer deposition (ALD) processes in which boron-containing, nitrogen-containing and tungsten-containing reactants are sequentially pulsed into a reaction chamber to deposit the WBN films. In some embodiments, the processes include multiple cycles of boron-containing, nitrogen-containing and tungsten-containing reactant pulses, with each cycle including multiple boron-containing pulses.
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1. A method comprising:
performing multiple cycles of sequentially introducing pulses of a boron-containing reactant, a nitrogen-containing reactant and a tungsten-containing reactant into a reaction chamber containing a semiconductor substrate to thereby deposit a ternary tungsten boride nitride film on the substrate, wherein the ternary tungsten boride nitride film contains tungsten-boron bonds and tungsten-nitrogen bonds, wherein a ratio of the number of boron-containing reactant pulses to the number of tungsten-containing reactant pulses introduced during the multiple cycles is at least three, and wherein the boron-containing reactant reduces the tungsten-containing reactant to form tungsten and provides boron to form the ternary tungsten boride nitride film.
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This application claims benefit under 35 USC § 119(e) of the following applications: U.S. Provisional Patent Application No. 61/676,123, filed Jul. 26, 2012 and U.S. Provisional Patent Application No. 61/697,775, filed Sep. 6, 2012. Both of these applications are incorporated herein by reference in their entireties.
Resistivity is an intrinsic property of a material and a measurement of a material's resistance to the movement of charge through the material. High or low resistivity materials can be used for different applications. For example, low resistivity metal layers in integrated circuits minimize power losses. High resistivity metal layers may be used as heater elements for phase change memory or other applications.
In one example, tungsten layers may be used as low resistivity electrical connections in the form of horizontal interconnects, vias between adjacent metal layers, and contacts between a first metal layer and the devices on the silicon substrate. Tungsten nitride layers may be used as diffusion barriers for tungsten interconnects, vias and plugs, providing relatively low resistivity and good adhesion to dielectric layers. Problems regarding the use of low resistivity tungsten layers with tungsten nitride layers, however, have prevented these materials from being used together in semiconductor devices.
Ternary tungsten boride nitride (WBN) thin films and related methods of formation are provided. The films have excellent thermal stability, tunable resistivity and good adhesion to oxides. Methods of forming the films can involve thermal atomic layer deposition (ALD) processes in which boron-containing, nitrogen-containing and tungsten-containing reactants are sequentially pulsed into a reaction chamber to deposit the WBN films. In some embodiments, the processes include multiple cycles of boron-containing, nitrogen-containing and tungsten-containing reactant pulses, with each cycle including multiple boron-containing pulses.
The following detailed description can be more fully understood when considered in conjunction with the drawings in which:
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention, which pertains to tungsten boride nitride films and methods of forming the same. Modifications, adaptations or variations of specific methods and of structures shown herein will be apparent to those skilled in the art and are within the scope of this invention.
Resistivity is an intrinsic property of a material and a measurement of a material's resistance to the movement of charge through the material. High or low resistivity materials can be used for different applications. For example, low resistivity metal layers in integrated circuits minimize power losses. High resistivity metal layers may be used as heater elements for phase change memory or other applications.
In one example, tungsten layers may be used as low resistivity electrical connections in the form of horizontal interconnects, vias between adjacent metal layers, and contacts between a first metal layer and the devices on the silicon substrate. Tungsten nitride layers may be used as diffusion barriers for tungsten interconnects, vias and plugs, providing relatively low resistivity and good adhesion to dielectric layers. Problems regarding the use of low resistivity tungsten layers with tungsten nitride layers, however, have prevented these materials from being used together in semiconductor devices.
Described herein are ternary tungsten boride nitride (WBN) thin films and related methods of formation. The films have excellent thermal stability, tunable resistivity and good adhesion to oxides. Methods of forming the films can involve thermal atomic layer deposition (ALD) processes in which boron-containing, nitrogen-containing and tungsten-containing reactants are sequentially pulsed into a reaction chamber to deposit the WBN films. In some embodiments, the processes include multiple cycles of boron-containing, nitrogen-containing and tungsten-containing reactant pulses, with each cycle including multiple boron-containing pulses. According to various embodiments, the WBN films can be barrier layers for tungsten interconnects and lines, thin film resistive heater elements for applications such as phase change memory or inkjet printers, and layers in a gate electrode stack.
In some embodiments, the methods described herein involve an atomic layer deposition (ALD) process. The process is repeated in a cyclical fashion until the desired thickness is achieved. ALD deposition, in general, is a method of sequentially depositing a plurality of atomic-scale layers on a wafer surface by sequentially injecting and removing reactants into and from a chamber. The reactants can be physically and/or chemically adsorbed onto the surface of a substrate in the chamber and/or react with a previously-adsorbed layer of one or more reactants. In embodiments described herein, pulses of reactants are sequentially injected into and purged from a reaction chamber to form a WBN thin film. As used herein, ALD broadly embodies any cyclical process of sequentially adding reactants for reaction on a substrate. In some embodiments, the ALD processes described herein are thermal ALD processes. Thermal ALD processes are non-plasma processes. In some cases, the activation energy for the surface reactions is provided solely via thermal energy. In some other instances, one or more forms of additional energy, e.g., UV radiation, may be used.
According to various embodiments, the methods involve multiple boron-containing reactant doses in each ALD process cycle to provide sufficient boron with which a tungsten containing precursor can react. In some embodiments, the methods involve multiple boron-containing and multiple nitrogen-containing reactant doses in each ALD process cycle. The W, B, and N ratios in the film can be modulated to achieve desired resistivity and other film characteristics.
First turning to
Excess reactant and byproduct can be purged or evacuated from the deposition chamber after block 103. As described below, in some embodiments, a relatively long purge dose is performed after block 103. The process continues with pulsing a nitrogen-containing reactant into the deposition chamber (105). Examples of suitable nitrogen-containing reactants include N2, NH3, and N2H4. Without being by a particular reaction, at least some of the nitrogen-containing reactant may react with the adsorbed boron-containing reactant to form BxN. Some amount of boron-containing reactant remains to react with a tungsten-containing reactant. In the case of using NH3 or N2H4, higher order boranes BxHy such as B6H10 that can react with the tungsten-containing reactant may be formed. Boron itself may also be available to react with the tungsten-containing reactant. Excess reactant and byproduct can be purged or evacuated from the deposition chamber after block 105. If an inert purge gas is used, example flow rates range from 5 slm to 100 slm, depending on the deposition chamber volume.
At block 107, if the blocks 103 and 105 have been performed n times, the process continues to block 109. If not, the process returns to block 103 with another pulse of a boron-containing reactant. The variable n is an integer greater than 1, and typically at least 3, though in some cases two repetitions of blocks 103 and 105 may suffice. Once blocks 103 and 105 have been performed n times, the process continues with pulsing a tungsten-containing reactant into the deposition chamber (109). Any process-compatible tungsten containing reactant may be used including WF6, WCl6, and W(CO)6. In some embodiments, the tungsten-containing reactant can be an organo-tungsten precursor. Examples of organo-tungsten precursors include bis(alkylimino)bis(alkylamino) compound such as bis(tert-butylimino) bis(dimethylamino) tungsten. The tungsten-containing reactant is reduced, forming the ternary WBN film. Excess reactant and byproduct can be purged or evacuated from the deposition chamber after block 109. This completes one cycle of a multi-cycle deposition. If additional thickness is desired (block 111), the process returns to block 103, with the counter in block 107 typically reset to zero such that the next cycle also includes multiple sub-cycles of boron-containing/nitrogen-containing reactant pulses. The order of certain operations in
Once block 203 has been performed n times such that the substrate has been exposed to n pulses of the boron-containing reactant, the process continues with pulsing a tungsten-containing reactant into the deposition chamber (207). The tungsten-containing reactant is reduced by the adsorbed boron-containing reactant to form tungsten. Unlike reducing agent starved regimes used to form metallic tungsten or tungsten nitride films in which the reducing agent is substantially consumed in its entirety, boron remains in the film. Excess reactant and byproduct can be purged or evacuated from the deposition chamber after block 207. The process continues with pulsing a nitrogen-containing reactant into the deposition chamber to form the WBN film (209). This completes one cycle of a multi-cycle deposition. If additional thickness is desired (block 211), the process returns to block 203, with the counter in block 205 typically reset to zero such that the next cycle also includes multiple sub-cycles of boron-containing reactant pulses. The order of certain operations in
The above-described processes involve exposing the substrate to more boron-containing reactant than tungsten-containing reactant to allow significant boron incorporation into the film. In some embodiments, this involves a ratio of the number of boron-containing reactant pulses to tungsten-containing reactant pulses of at least 2:1. The ratio can be at least 3:1, 4:1 or higher according to various embodiments. In the processes described herein, a pulse can be a single injection of gas or several short sequential injections. In some embodiments, the processes involve a ratio of the number of boron-containing reactant injections to tungsten-containing reactant injections of at least 2:1, 3:1 or higher.
In some embodiments, the relative flow rates of the pulses may also be varied to modulate the concentrations of W, B, and N. Example flow rates can range from about 60 sccm to about 300 sccm for a 300 mm wafer, with flow rates scaling linearly with area. Dosage times can also be varied, a greater number of short pulses of the boron-containing reactant provide more efficient boron incorporation than fewer, longer pulses. Moreover, in some embodiments, a relatively long purge time follows at least the pulses of the boron-containing reactant. In some embodiments, the purge time is at least about 5 times than that of the boron-containing reactant. In some embodiments, the purge time is at least about 10 times or even 15 times than that of the boron-containing reactant. For example, a purge of 7 seconds may follow a boron-containing reactant dose of 0.5 seconds. Without being bound by a particular theory, it is believed that it removing substantially all byproduct during the purge can significantly aid boron incorporation. Lower purge:boron-containing reactant dose time ratios may be used, for example, if the purge has substantially higher flow rates and pressures. WBN film fabrication can be performed within a wide range of temperatures. According to various embodiments, it can done at less than 300 C wafer temperature (e.g. 275 C), or up to >400 C temperature.
The relative amounts tungsten, boron and nitrogen in the WBN films, and thus their physical, electrical, and chemical characteristics can be efficiently tuned by varying the number of sub-cycles (i.e., the number n) in the processes described above. The process described in
The films deposited by the processes described with reference to
Applications
Below are descriptions of various example applications of the ternary WBN films. Note that these descriptions are presented only as examples. They are not meant to exclude other applications nor are they meant to exclude the use of the invention from variations or combinations of methods described.
The thermal ALD WBN deposition methods can be used in processes for generating tungsten plugs for contact or via fill in IC wafer fabrication. The WBN layer serves as a diffusion barrier for the tungsten contact, and can also serve as a liner or adhesion layer. The WBN barrier and/or adhesion layer for direct tungsten plugfill contacts tungsten, metal silicides (such as TiSix, CoSix, NiSix, or WSix), silicon (N+ or P+), or other electrically conductive materials. Because WBN film fabrication can be performed at low wafer temperature (e.g. 275 C), it can also be used in some special applications, for example, magnetoresistive random access memory (MRAM), where low process temperature is required to avoid device degradation or functional materials damage.
In some embodiments, the WBN layer can be part of an integrated contact plug film stack including WBN (barrier-adhesion layer)/pulsed nucleation layer W (PNL-W) (nucleation layer)/CVD-W (primary conductor and bulk plugfill). PNL-W nucleation layers are described in U.S. Pat. Nos. 7,005,372; 7,262,125; 7,589,017; 7,772,114; and 8,058,170, which are incorporated by reference herein.
In the example depicted in
Additional discussion regarding PNL type processes to deposit tungsten nucleation layers can be found in above-referenced U.S. Pat. No. 7,589,017, which describes depositing PNL-W nucleation layers at relatively low temperatures, e.g., 300° C. After deposition, the tungsten nucleation layer can be treated to lower its resistivity. Possible treatments include exposure of the tungsten nucleation layer to pulses of reducing agent, such as a silane or a borane (e.g., diborane), or a high temperature treatment. Low resistivity treatments are described in above-referenced U.S. Pat. Nos. 7,589,017; 7,772,114; and 8,058,170 and in U.S. patent application Ser. No. 12/755,248, which is incorporated by reference herein.
After the desired tungsten nucleation layer thickness is attained and treated, bulk tungsten is deposited on the nucleation layer with CVD (505). Any suitable CVD process with any suitable tungsten-containing precursor may be used. In certain embodiments the tungsten precursor is one of WF6, WCl6 and W(CO)6. Frequently, the CVD process is performed using a mixture of molecular hydrogen and one or more of these precursors. In other embodiments, the CVD process may employ a tungsten precursor together with silane, a mixture of hydrogen and silane, or a mixture of hydrogen and borane (such as diborane). Non-CVD process can also be employed to form the tungsten bulk layer. These include ALD, PNL, or PVD. The resistivity of a tungsten layer (i.e., tungsten nucleation layer and tungsten bulk layer) deposited with the low-resistivity tungsten process is from about 10 μΩ-cm to about 30 μΩ-cm, but the resistivity does depend on the thickness of the layer.
The tungsten bulk layer can be deposited to any thickness. Tungsten interconnect lines for integrated circuit applications may have a total thickness (tungsten nucleation layer and tungsten bulk layer) of between about 20 Å and 1,000 Å. For a typical bit line, the total tungsten layer thickness is typically no greater than about 500 Å.
Conventional film stacks for tungsten vias and contacts include Ti/TiN/W nucleation/CVD-W. The ternary WBN films can be used to simplify this stack to WBN/PNL-W (nucleation)/CVD-W as described with reference to
Moreover, WBN/low resistivity W may have advantages over WN/low resistivity tungsten. Low resistivity tungsten can achieve low resistivity by increasing W grain size. However, increasing grain size can require stronger adhesion between the barrier layer and the oxide layer to undergo CMP without coring, opening, or detachment of the barrier layer from the oxide. Low resistivity nucleation processes that use boron-containing reducing agents (e.g., as described in the above-referenced patents and patent application) on WN barrier layers have adhesion problems. As described further below, the ternary WBN films described herein show improved adhesion to oxide over thermal ALD WN film.
WBN can be formed in the vias or contact holes directly on the dielectric or with a PNL-W seed layer. The tungsten bulk layer may be deposited by PNL, ALD, CVD, or a combination of these. Also, the process may be integrated with a degas and/or preclean operation (e.g., a plasma etch) prior to the WBN deposition. In some cases it may be advantageous to create a combined TiN/WBN barrier layer.
The reactor employed for this application may support single-wafer processing or multi-station sequential deposition, with WBN and tungsten CVD integrated in a single module. In some implementations wafer pre-heat, preclean, and WBN deposition are combined in a one multi-station process module and a second process module is dedicated to the deposition of PNL-W and CVD-W. In some situations wafer preheat/degas, and wafer preclean may each be given independent process modules on an integrated cluster tool to provide greater process flexibility.
Example process flows include the following:
Note that “DFE” is Dual Frequency Etch. As an example, NOVA wafer preclean manufactured by Lam Research® Corporation uses Ar ions from a dual frequency inductive plasma to provide high plasma density (low frequency component) and independently controllable ion acceleration (high frequency component).
In another application, the ternary WBN films described herein can be used as a metal electrode either alone or in a WBN/W film stack. More generally, the WBN layer can function as an adhesion layer, barrier layer, and/or as a primary electrical conductor for a top or bottom capacitor electrode. High electrode work functions are known to reduce leakage in memory cell capacitors. In the methods described herein, N level and thus work function can be tuned as described above. The tungsten may be deposited by PNL, ALD, CVD, or a combination thereof. Degas and/or preclean may be employed. And single wafer processing or multi-station sequential deposition may be employed.
Note that integrated circuit capacitor electrodes are currently made from film stack of CVD-TiN and highly doped polysilicon. The deposition temperatures for TiCl4-based CVD-TiN and poly silicon are >550 C and >600 C, respectively. These high temperatures result in the driving of impurities into the capacitor dielectric (e.g. Cl) and the oxidation of the TiN barrier layer, both of which reduce capacitance and increase capacitor leakage. A WBN-W capacitor electrode can dramatically reduce the manufacturing thermal cycles with resulting leakage reductions and improvements or post anneal capacitance for comparable leakage. The following process flows can be used to deposit top or bottom capacitor electrodes.
1) WBN/PNLW nucleation layer/CVD-W
2) WBN/PNL-W/CVD-W
3) WBN-CVD-W plugfill
4) WBN-W integrated with degas, preclean (DFE or reactive clean)
The capacitors may be trench capacitors, fin capacitors, plate capacitors or any other structure suitable for IC applications. In the case of stacked capacitors the bottom electrode may be deposited on a polysilicon bottom electrode to facilitate structure formation. The extremely high step coverage of the ternary WBN and PNL-W are enabling features required for implementation of WBN for modern semiconductor memory cell electrodes.
In another example application, WBN functions as an adhesion layer, barrier layer, or primary conductor in a gate electrode. WBN may be applied directly on the gate dielectric or on a polysilicon electrode to reduce polysilicon line thickness requirements.
Some characteristics for a transistor gate application include a tunable work function, thermal stability, and resistance to oxidation. Modifying the WBN stoichiometry of the as-deposited film can tune the work function of the WBN film. As a gate electrode, a WBN or WBN/W film stack provides a metal gate that resists the charge depletion phenomenon commonly observed in non-metallic gate electrodes such as those fabricated from polysilicon. Charge depletion effectively increases the gate dielectric thickness. A W/WBN gate electrode may also be formed on top of a polysilicon gate electrode to reduce the height requirement of the polysilicon gate without changing the gate dielectric/polysilicon interface.
As discussed above, it may be valuable to fabricate layered PNL-W/PNL-WN gate electrode structures to facilitate work function modulations for mixed N+ and P+ transistor devices.
Various possible process flow implementations include
Tool configuration options include
In another example application, the ternary WBN films described herein can be used as resistive elements. One application of resistive heating elements is in a phase change memory cell, an example of which is shown in
Phase change material 660 is typically a chalcogenide glass material, though other materials that are capable of changing from a crystalline to an amorphous state or vice versa upon application or withdrawal of heat may also be used. Because the electrical resistivity of the amorphous state of the chalcogenide material is significantly higher than the crystalline state, the phase change material can be used to store data. The amorphous, highly resistive state is used to represent one bit value (0 or 6) with the crystalline, low resistive state used to represent the other bit value.
Conductive layer 610 may be an address line, e.g., a column line, row line, bit line or word line, used to program or read information stored using the phase change material. The conductive layer may be connected to external addressing circuitry.
The electrodes are made of electrically conductive materials. In the example shown in
The ternary WBN heater element 650 is generates heat in response to the electrical current passing through the adjacent electrode, lower electrode 630. The resistivity of ternary WBN heater element 650 is high relative to that of electrode 630 to generate heat from the current. In operation a current or voltage pulse is applied to the heater element to generate heat. The heat generated by the heater element heats the phase-change material to a temperature above its crystallization temperature and below its melting temperature to achieve a crystalline state, which typically represents a bit value of 6. To change the phase change material back to its amorphous state, the heater element heats the material above its melting point. The phase change material is then quenched to achieve an amorphous state, which typically represents a bit value of 0. The ternary WBN films can have high resistivity (e.g., around 5000 μΩ-cm for a 50-60 angstrom film) and are stable on anneal to 900° C. and have electric contact to the underlying surface (e.g., the tungsten plug electrode in
Other applications including a barrier and adhesion layer for the deposition of bitline or wordline local interconnects in DRAM devices. In another application the WBN film can serve as an adhesion layer for W deposition on oxide in semiconductor applications such as light shield for CCD devices.
Apparatus
Also mounted on the transfer module 703 may be one or more single or multi-station modules 705 capable of performing plasma or chemical (non-plasma) pre-cleans. The module may also be used for various other treatments, e.g., post-deposition nitriding treatments. The system 700 also includes one or more (in this case two) wafer source modules 701 where wafers are stored before and after processing. An atmospheric robot (not shown) in the atmospheric transfer chamber 719 first removes wafers from the source modules 701 to loadlocks 721. A wafer transfer device (generally a robot arm unit) in the transfer module 703 moves the wafers from loadlocks 721 to and among the modules mounted on the transfer module 703.
In certain embodiments, a system controller 750 is employed to control process conditions during deposition. The controller will typically include one or more memory devices and one or more processors. The processor may include a CPU or computer, analog and/or digital input/output connections, stepper motor controller boards, etc.
The controller may control all of the activities of the deposition apparatus. The system controller executes system control software including sets of instructions for controlling the timing, mixture of gases, chamber pressure, chamber temperature, wafer temperature, RF power levels, wafer chuck or pedestal position, and other parameters of a particular process. Other computer programs stored on memory devices associated with the controller may be employed in some embodiments.
Typically there will be a user interface associated with the controller. The user interface may include a display screen, graphical software displays of the apparatus and/or process conditions, and user input devices such as pointing devices, keyboards, touch screens, microphones, etc.
The computer program code for controlling the deposition and other processes in a process sequence can be written in any conventional computer readable programming language: for example, assembly language, C, C++, Pascal, Fortran or others. Compiled object code or script is executed by the processor to perform the tasks identified in the program.
The controller parameters relate to process conditions such as, for example, process gas composition and flow rates, temperature, pressure, plasma conditions such as RF power levels and the low frequency RF frequency, cooling gas pressure, and chamber wall temperature. These parameters are provided to the user in the form of a recipe, and may be entered utilizing the user interface.
Signals for monitoring the process may be provided by analog and/or digital input connections of the system controller. The signals for controlling the process are output on the analog and digital output connections of the deposition apparatus.
The system software may be designed or configured in many different ways. For example, various chamber component subroutines or control objects may be written to control operation of the chamber components necessary to carry out the inventive deposition processes. Examples of programs or sections of programs for this purpose include substrate positioning code, process gas control code, pressure control code, heater control code, and plasma control code.
A substrate positioning program may include program code for controlling chamber components that are used to load the substrate onto a pedestal or chuck and to control the spacing between the substrate and other parts of the chamber such as a gas inlet and/or target. A process gas control program may include code for controlling gas composition and flow rates and optionally for flowing gas into the chamber prior to deposition in order to stabilize the pressure in the chamber. A pressure control program may include code for controlling the pressure in the chamber by regulating, e.g., a throttle valve in the exhaust system of the chamber. A heater control program may include code for controlling the current to a heating unit that is used to heat the substrate. Alternatively, the heater control program may control delivery of a heat transfer gas such as helium to the wafer chuck.
Examples of chamber sensors that may be monitored during deposition include mass flow controllers, pressure sensors such as manometers, and thermocouples located in pedestal or chuck. Appropriately programmed feedback and control algorithms may be used with data from these sensors to maintain desired process conditions.
The foregoing describes implementation of embodiments of the invention in a single or multi-chamber semiconductor processing tool.
Thermal stability of the WBN film is also improved over WN films. Table 1 below shows atomic concentration of the WBN films after two 30 minute anneals at 850° C. A normal WN film (e.g., about 50% W, 50% N) would become almost pure W after being annealed at these conditions.
TABLE 1
WBN film composition pre- and post-thermal annealing
W
B
N
Density (at/cc)
Pre-anneal
29.3
43.1
27.6
1.16E+23
Post-anneal
44.6
29.6
24.8
1.05E+23
Unlike with WN films, which are subject to nitrogen loss at temperatures greater than about 700° C., almost no N loss is observed after 1 hour of high temperature anneal in the WBN films. Thermal stability is an important characteristic for barrier films.
A 4-point bend analysis of a 60 Å WBN film shows improved adhesion to oxide over WN film. TEOS oxide was deposited on a silicon substrate. A 60 Å WBN film/1500 Å low resistivity W film stack was deposited on the TEOS, using the following process:
An epoxy layer was applied on the W and a cut was made in the WBN/W stack, with a four point bend applied. The failing interface was observed between the tungsten and the epoxy, with the WBN film remaining adhered to the oxide. WN films tend to delaminate on oxide in a similar 4 point bend test.
Chemical mechanical planarization (CMP) was performed on WBN/W vias in oxide filled by the same method described above. A SEM top view of the vias after CMP showed 1) the features remain filled indicating no tungsten pulled out, and 2) no contrast due to a recessed WBN barrier film. This also is an improvement over WN/W vias that show defects after CMP.
Without being bound by a particular theory, it is believed that the good adhesion of WBN on oxide may be due to 1) multiple boron pulses and high temperature allow strong B—O bond formation at the oxide/WBN interface; and (2) the good barrier property of WBN films effectively prevents fluorine or other impurities from the CVD W process diffuse into the oxide interface and affect adhesion. However, as described above the method described in
As indicated above, the level of N in the film and thus the resistivity can be modulated. Table 2 below shows resistivity of ternary WBN films deposited on 5 k Å TEOS oxide using multiple cycles of an n(B2H6→1 NH3)→WF6 process sequence as described above with reference to
TABLE 2
Modulating N level and resistivity
n, number of B2H6 → NH3
XRF thickness of
sub-cycles per ALD cycle
WBN film, Å
Resistivity, μΩ-cm
1
85.4
446.5
2
86.8
708.2
3
85.4
1010.2
4
78.0
2022.9
5
67.8
6382.9
Table 2 shows that the resistivity can be modified by changing the number of B2H6→1 NH3 sub-cycles. Higher resistivity indicates a greater nitrogen level within the ternary WBN film. Moreover, the work function of the film can be modified by appropriately tuning the nitrogen level.
The apparatus/processes described herein may be used in conjunction with lithographic patterning tools or processes, for example, for the fabrication or manufacture of semiconductor devices, displays, LEDs, photovoltaic panels, and the like. Typically, though not necessarily, such tools/processes will be used or conducted together in a common fabrication facility. Lithographic patterning of a film typically comprises some or all of the following steps, each step enabled with a number of possible tools: (1) application of photoresist on a work piece, i.e., substrate, using a spin-on or spray-on tool; (2) curing of photoresist using a hot plate or furnace or UV curing tool; (3) exposing the photoresist to visible or UV or x-ray light with a tool such as a wafer stepper; (4) developing the resist so as to selectively remove resist and thereby pattern it using a tool such as a wet bench; (5) transferring the resist pattern into an underlying film or work piece by using a dry or plasma-assisted etching tool; and (6) removing the resist using a tool such as an RF or microwave plasma resist stripper.
There are many alternative ways of implementing the methods and apparatus of the disclosed embodiments. It is therefore intended that the following appended claims be interpreted as including all such alterations, modifications, permutations, and substitute equivalents as fall within the true spirit and scope of the disclosed embodiments.
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